“The survival curves become close to never-smokers,” said Dr. Prabhat Jha, head of St. Mike’s Centre for Global HealthResearch.

“You’re still at a disadvantage by quitting at age 40, but those that quit by age 30 have pretty much the same survival curves as never-smokers,” according to Jha, a public health expert at the University of Toronto whose study was published Wednesday by the New England Journal of Medicine.

Cigarettes statistically cut a decade off a smoker’s life, Jha said. But those who quit at 40 can gain back nine of those lost years.

Currently, life expectancies sit around 80 years for the large majority of non-smoking 25-year-olds in North America. Some 70 per cent of women and 60 per cent of men will reach their eighties.

Similar majorities of people who quit the weed at 40 can expect to live to 79, Jha said.

Such statistics, Jha concedes, will surely encourage some younger smokers to hang fire on quitting during their more reckless years.